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Topic: more on the c5 fork. (Read 1686 times)

i read the write up on removal of the fork.saturday while the power was out i had nothing to do so i read through parts of my service manual.i am planning to relace the fork oil as the bike has 4500 miles on it now.so my questions are:the book talks about a drain plug on the c5 and i checked both forks and there is an allen bolt on the underside of the fork just behind where the axel is.can i just drain it there and open the top with a 12mm allen without removing the forks?

I am planning to get my C5's fork oil replaced. Which oil(5w/10w/15w/20w) would you recommend as the best fork oil for a C5 which is ridden on the good and bad roads in India? I plan to get the fork oil replaced once, and for a very long time. Do you recommend a change of fork oil seals too?

Since you have to remove them to fill, you may as well drain that way too. No need to break loose the little allen on the bottom of the fork that holds the damper rod. On occasion it's a pain to loosen and/or a pain to tighten back up. Just leave it.

C5 manuals says each fork gets 195ml. Should I refill with 195 ml or lesser(180-185ml)? Any probability of the seals blowing off with full 195ml in each fork? You have suggested 10W fork oil. How about other grades like 5W,15W and 20W. Motul dealer in my city stocks all grades of fully synthetic fork oil, from 5W to 20W. Is fully synthetic better for forks or mineral would do fine as well?

Synthetic is less affected by cold temps. Forks tend to feel stiffer in very cold tempsas the oil gets thicker. Synthetic oil gets thicker when it's cold, but not as much as Dino oils. And it lasts a little longer. The advantages are not enough to pick it over the proper weight dino oil, go with regular if you can't get 10w synth.

I put 5w in my fork and moved the leg, you could barely feel any damping. I'm a fan if light damping but that was almost none at all. Going heavier means the fork will be less reactive and will transmit more shock to your hands. It may stop the initial dive a bit on braking but an extended stop will push the forks down just as far. IMO heavier fork oil is usually a cheat that covers problems that should be fixed another way, usually more preload or stiffer springs.

Just go with 195ml of 10w in each leg, you'll be amazed at the difference. If you doubt it, check Barenekd's recent post. He rides hard, pushing the bike to the limit and beyond. The right amount of 10w oil made his bike feel way better.

I understand from numerous writeups that the C5 forks need to removed for replacing fork oil. However I am just wondering if it was not possible to fill oil through the drain hole itself by turning the fork upside down, rather than dismantling it completely ??

It's not a fill hole, it's not even really a drain hole. It's the bolt that holds the damper rod and if you loosen it a little you can drain the oil through it even though that's not what it's for. It's really not going to work as a fill hole. Plus, whatever you do to "turn the fork over" is going to involve removing the fork legs anyway.

Once the leg is off you don't need to take it apart, you just need to remove the top cap. The spacer, washer, and spring come out. You turn it upside down and pump it while draining all the oil, add new oil, pump it some more to get the bubbles out, put the spring, washer, and spacer back, and put the top cap back on.

There seem to be a lot of questions. I know the original is a REALLY long post but please read it. Then read it again. Then leave it for a day, then go read it a third time. There's a lot of info there but it's all there. Take the time to read and absorb it.

There seem to be a lot of questions. I know the original is a REALLY long post but please read it. Then read it again. Then leave it for a day, then go read it a third time. There's a lot of info there but it's all there. Take the time to read and absorb it.

I have read your write-up a number of times, Scott, and it's very much appreciated! One thing I still haven't sorted out in my mind, due to my mind and not your write-up, is at what point, if I'm only changing the oil, do I stop following your procedure and reverse it. I can't remember, you may even say, "At this point, if you're only changing the oil, stop following this procedure and reverse it." And yes, I'll be reading it again!

I'll be doing it within the next couple of months while my bike hibernates...

Synthetic is less affected by cold temps. Forks tend to feel stiffer in very cold tempsas the oil gets thicker. Synthetic oil gets thicker when it's cold, but not as much as Dino oils. And it lasts a little longer. The advantages are not enough to pick it over the proper weight dino oil, go with regular if you can't get 10w synth.

I put 5w in my fork and moved the leg, you could barely feel any damping. I'm a fan if light damping but that was almost none at all. Going heavier means the fork will be less reactive and will transmit more shock to your hands. It may stop the initial dive a bit on braking but an extended stop will push the forks down just as far. IMO heavier fork oil is usually a cheat that covers problems that should be fixed another way, usually more preload or stiffer springs.

Just go with 195ml of 10w in each leg, you'll be amazed at the difference. If you doubt it, check Barenekd's recent post. He rides hard, pushing the bike to the limit and beyond. The right amount of 10w oil made his bike feel way better.

Scott

Thanks Scott!

10W Fully Synthetic is available in my city. I will change the fork oil next weekend. Hope that things go well with the bad roads here in India.